Listing 3. Goodness Function

/* linux/kernel/sched.c
* This is the function that decides how desirable a process is.
* You can weigh different processes against each other depending
 * on what CPU they've run on lately etc to try to handle cache
 * and TLB miss penalties.
 *
 * Return values:
 *	 -1000: never select this
 *	     0: out of time, recalculate counters (but it might still
 *	     be
 *		selected)
 *	   +ve: "goodness" value (the larger, the better)
 *	 +1000: realtime process, select this.
 */
static inline int goodness(struct task_struct * p, int this_cpu, struct
mm_struct *this_mm)
{
	int weight;
	/*
	 * Realtime process, select the first one on the
	 * runqueue (taking priorities within processes
	 * into account).
	 */
	if (p->policy != SCHED_OTHER) {
		weight = 1000 + p->rt_priority;
		goto out;
	}
	/*
	 * Give the process a first-approximation goodness value
	 * according to the number of clock-ticks it has left.
	 *
	 * Don't do any other calculations if the time slice is
	 * over..
	 */
	weight = p->counter;
	if (!weight)
		goto out;
			
#ifdef __SMP__
	/* Give a largish advantage to the same processor...  */
	/* (this is equivalent to penalizing other processors) */
	if (p->processor == this_cpu)
		weight += PROC_CHANGE_PENALTY;
#endif
	/* .. and a slight advantage to the current MM */
	if (p->mm == this_mm)
		weight += 1;
	weight += p->priority;
out:
	return weight;
}